/*
 *  Copyright 2013 National Institute of Advanced Industrial Science and Technology
 *  
 *  Licensed under the Apache License, Version 2.0 (the "License");
 *  you may not use this file except in compliance with the License.
 *  You may obtain a copy of the License at
 *  
 *      http://www.apache.org/licenses/LICENSE-2.0
 *  
 *  Unless required by applicable law or agreed to in writing, software
 *  distributed under the License is distributed on an "AS IS" BASIS,
 *  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 *  See the License for the specific language governing permissions and
 *  limitations under the License.
 */

package org.sss.common.io;

import java.io.IOException;
import java.util.Iterator;
import java.util.List;

import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.sss.common.DataReceiver;
import org.sss.common.KeyValues;
import org.sss.mapreduce.Configuration;
import org.sss.mapreduce.GroupID;
import org.sss.mapreduce.SssException;
import org.sss.mapreduce.StorageNode;
import org.sss.util.BytesComparator;

public class StreamDBKeyValuesReader extends AbstractKeyValueReader {
  private static BytesComparator CMP = new BytesComparator();
  @SuppressWarnings("unused")
  private static Logger logger = LoggerFactory.getLogger(StreamDBKeyValuesReader.class);

  public StreamDBKeyValuesReader(Configuration conf,
                                 StorageNode node,
                                 GroupID source,
                                 int subhash,
                                 DataReceiver<List<KeyValues>> next) throws SssException {
    super(conf, node, source, subhash, next);
  }

  @Override
  protected void doRead(IOThread iot) throws SssException, IOException, InterruptedException {
    assert getSource() != null: "source should not be null";
    StreamDB sdb = iot.getStreamDB(node);
    int limitNBytes = iot.getIOGetLimitNBytes();

    Iterator<byte[]> it = sdb.read(getSource(), subhash, isDestructiveRead()).iterator();
    KeyValuesQueue kvq = new KeyValuesQueue(next, limitNBytes);
    try {
      byte[] prevKey = null;
      while (it.hasNext()) {
        checkCanceled();

        byte[] key = it.next();
        byte[] val = it.next();
        countup(1, key.length + val.length);

        if (prevKey == null || CMP.compare(key, prevKey) != 0) {
          kvq.pushKey(key);
          prevKey = key;
        }
        kvq.pushValue(val);
      }
    }
    finally {
      kvq.pushEnd();
    }
  }
}
